1. Field of the Invention
The present invention relates generally to the field of telephony. More specifically, the present invention discloses a telecommunication system that provides automatic switching between a voice mode and a variety of data modes.
2. Statement of the Problem
The present invention is intended to address the problem of communicating both voice and data by telephone over a single conventional telephone line. It is often desirable to be able to transmit data over a single telephone line interspersed with verbal discussions between the parties. This data can be in the form of visual images relevant to the conversation. For example, a travel agent might wish to show a telephone customer a travel itinerary as they discuss it, or a broker might want to show a customer a visual confirmation of a financial transaction that the customer has just made orally over the telephone. Image data can be transmitted over a telephone line, for example, using conventional facsimile machines or the VoiceView.TM. products marketed by Radish Communications Systems, Inc. of Boulder, Colo. Alternatively, this data can be in the form of one or more data files to be transferred by modem between the parties' computers.
A number of telephone systems have been invented in the past to allow transmission of both voice and data over a single telephone line by switching between a voice mode and a single data mode, including the following:
______________________________________ Inventor U.S. Pat. No. Issue Date ______________________________________ Davis 5,164,982 Nov. 17, 1992 Emmons et al. 4,932,047 June 5, 1990 Yoshida 4,815,121 Mar. 21, 1989 Cooper-Hart et al. 4,715,059 Dec. 22, 1987 Dumas 4,656,654 April 7, 1987 Artom 4,387,271 June 7, 1983 ______________________________________
Davis discloses a telecommunications display system for accommodating both voice and data over a single telephone line. The receiving party ("subscriber") is provided with a display terminal 14 that is connected to the telephone line 22, 52 between the telephone network 50 and the base of the user's telephone 12 as shown in FIG. 1 of U.S. Pat. No. 5,164,982. The display terminal includes a voice/data selector that can automatically recognize digital data and switches from voice communication to data communication modes. This patent discusses one embodiment of the VoiceView.TM. products marketed by Radish Communications Systems, Inc.
Emmons et al. disclose an example of a conversational video phone. The device communicates both audio signals and freeze-frame video images over a standard telephone line.
Yoshida discloses a telephone communication system that recognizes speech and automatically switches from data to speech transmission.
Cooper-Hart et al. disclose a conversational freeze-frame video phone that has been marketed by Luma Telecom, Inc. under the name "Luma." This system includes a camera for periodically capturing an image that is converted into digital data and transmitted over the telephone line to a remote unit in a single short burst. Audio transmission is interrupted upon detection of a video signal being transmitted. The data format and transmission rate for the video signal are fixed.
Dumas discloses a teleconferencing system that supports both audio and graphic communications. Each user has a personal computer (PC) with a smart modem that monitors the telephone line for a predetermined set of identification codes indicating that graphics are about to be sent by another conference participant. Here again, the data format appears to be fixed.
Artom discloses another example of a telephone system for combining voice and data communications over a single telephone line.
In addition to the prior art listed above, a number of modems and other telecommunications systems have been invented in the past that allow selection of multiple data formats or modes of communication that are established at the beginning of the call, including the following:
______________________________________ Inventor U.S. Pat. No. Issue Date ______________________________________ Pan 3,423,534 Jan. 21, 1969 Parikh et al. 4,168,469 Sep. 18, 1979 Cain et al. 4,621,366 Nov. 4, 1986 Grenzebach et al. 4,661,657 Apr. 28, 1987 Levine et al. 4,876,740 Oct. 24, 1989 Greszczuk 4,931,250 June 5, 1990 Walsh 5,202,899 Apr. 13, 1993 Shirai et al. 5,182,762 Jan. 26, 1993 Kloc et al. 5,241,565 Aug. 31, 1993 Berland 5,282,238 Jan. 25, 1994 ______________________________________
The patent to Parikh et al. shows a data communications adapter to permit communications using the Synchronous Data Link Control format (SDLC).
Greszczuk discloses a multimode modem that sends a sequence of handshake signals corresponding to a variety of modem types, and then configures itself to operate in the mode indicated by the response received from the far-end modem. Walsh discusses another example of a similar system.
The modem disclosed by Shirai et al. negotiates the data transmission rate and data compression technique with the far-end modem during the initial handshaking procedure. The remaining references are only of general interest.
Finally, a number of modems and other telecommunications systems have been invented in the past that allow modems to exchange information concerning various features or data rates that are supported during an initial handshaking protocol, including the following:
______________________________________ Inventor U.S. Pat. No. Issue Date ______________________________________ Hendrickson 4,001,504 Jan. 4, 1977 Bremer 4,663,766 May 5, 1987 Shih 4,727,370 Feb. 23, 1988 Copeland 4,782,498 Nov. 1, 1988 McGlynn et al. 4,905,282 Feb. 27, 1990 McGlynn et al. 4,953,210 Aug. 28, 1990 Hallman 5,146,472 Sept. 8, 1992 ______________________________________
The two patents to McGlynn et al. show a feature negotiation protocol for modems. The originating modem initiates negotiations by sending a list of supported features. The answering modem responds by confirming that all of the listed features are supported, by returning a subset of the features list, or by sending a different features list.
Copeland discusses a handshake procedure between modems for exchanging data such as device type, modes supported, speeds supported, signal quality conditions, etc.
The Walsh and Greszczuk patents listed previously are also relevant to this category of prior art. The modems described in these patents transmit an initial sequence of handshake signals corresponding to a variety of modem types. The modem then configures according to the response from the far-end modem.
The Bremer patent is an example of a modem with an automatic data rate selection feature. The remaining patents listed above are only of general interest.
3. Solution to the Problem
None of the prior art references show a telecommunication system providing automatic switching between voice and any of a plurality of data modes over a conventional telephone line using the present communications protocol. In particular, the present system allow the units to exchange information concerning their respective communications capabilities and the data modes that each unit supports. The units can then dynamically select different data modes throughout a conversation to transfer data in various formats.